Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N5/00—Details of television systems
  • H04N5/14—Picture signal circuitry for video frequency region
  • H04N5/21—Circuitry for suppressing or minimising disturbance, e.g. moiré or halo

Definitions

• This invention relates to video signal processing.
• a variety of filter and other processing techniques have been proposed for noise reduction purposes. Typically, these involve an averaging of the information at one pixel with that from surrounding pixels in one, two or three dimensions. A compromise is usually made betweeen adequate noise reduction and a loss of resolution which is within acceptable limits. A further difficulty arises when there is multi-generation processing of a video signal. If a video signal is filtered repeatedly, using the same or different noise reduction filters, there is a serious risk that the loss of resolution and any artifacts introduced by the filtering process, will increase with each filtering pass.
• the present invention consists, in one aspect, in a method of video signal processing wherein a first video signal is averaged with a second video signal advanced or retarded with respect to the first video signal by one field interval, in such manner that averaging is conducted only between fields belonging to the same video frame.
• the method according to the present invention is applicable to video material from various sources, including original video material and telecined film material.
• the averaging is disabled at high inter-field luminance differences. The assumption is made that high inter-field differences are less likely to have arisen from random noise.
• the averaging is restricted to high frequency luminance signal components.
• the present invention consists in video signal processing means comprising a field delay line for generating a first video signal, a second video signal advanced with respect to the first video signal by one field interval and a third video signal retarded with respect to the first video signal by one field interval; switch means controlled by the field repetition rate and averaging means for averaging the first video signal and, via the switch means, alternately the second video signal and the third signal, in such manner that averaging is conducted only between fields belonging to the same video frame.
• a high pass filter is provided such that averaging is conducted only at higher frequency signal components.
• Figure 1 is a block diagram illustrating a first embodiment of the present invention
• Figure 2 is a diagram illustrating the correspondence between video signals averaged in accordance with this invention.
• Figure 3 is a block diagram similar to Figure 1 and illustrating a modification
• Figure 4 is a block diagram similar to Figure 1 illustrating a further modification.
• the filter according to this invention comprises two delay units 10 and 12 each having a delay corresponding to one field interval.
• the delay is equal to 312H (H being one line interval) whilst in the NTSC mode the delay is equal to 263H.
• the midpoint of the two delays is taken to an adder 14 whilst a switcher 16 enables a second input to be provided to the adder 14 which is, alternatively, advanced or retarded by one field interval.
• the switcher is controlled at the field rate.
• Filters such as shown in Figure 1 may be provided for both luminance and chrominance channels, for luminance alone or for chrominance alone. The same approach can be adopted for composite signals.
• a still further advantage of the present invention lies in the elimination in chroma flicker arising from the misalignment of heads in replayed S-VHS.
• the present invention includes a modification in which the averaging process is disabled or modified in the case of large inter-field differences.
• the luminance field difference signal from the subtractor 18 is low passed in the filter 20.
• the second input to the lookup table 22 is the direct output of the subtractor 18.
• the output of the lookup table is, depending upon whether the field is odd or even, given by K(A-B)/2 or K(C-B)/2.
• K is a non-linear factor related to the luminance field difference. At small luminance field difference, factor K is set at or close to unity; field averaging occurs and the output of adder 14 is the same as in the embodiment of Figure 1. It is thus ensured that low contrast components such as noise and residual chrominance signals are suppressed.
• K is set close to zero; the averaging process is effectively diabled and the ouput of the adder 14 is simply the field B. Whilst the non-linear factor K is controlled through a luminance field difference signal, the averaging process may be applied both to luminance and chrominance information or even to composite signals.

Landscapes

• Engineering & Computer Science (AREA)
• Multimedia (AREA)
• Signal Processing (AREA)
• Picture Signal Circuits (AREA)
• Closed-Circuit Television Systems (AREA)
• Processing Of Color Television Signals (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

Family

ID=10718192

Family Applications (1)

Country Status (6)

Citations (5)

• 1992
  • 1992-07-03 GB GB929214219A patent/GB9214219D0/en active Pending
• 1993
  • 1993-07-05 AT AT93914873T patent/ATE175831T1/de not_active IP Right Cessation
  • 1993-07-05 AU AU45091/93A patent/AU4509193A/en not_active Abandoned
  • 1993-07-05 EP EP93914873A patent/EP0626120B1/de not_active Expired - Lifetime
  • 1993-07-05 DE DE69323068T patent/DE69323068T2/de not_active Expired - Fee Related
  • 1993-07-05 WO PCT/GB1993/001396 patent/WO1994001966A1/en active IP Right Grant

Patent Citations (5)

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